Receiving method and receiver

ABSTRACT

BB input units input baseband received signals. An initial weight data setting unit sets weighting coefficients to be utilized in the interval of a training signal as initial weighting coefficients. A gap compensating unit compensates control weighting coefficients with a gap error signal and outputs the updated weighting coefficients acquired as a result of the compensation. A weight switching unit selects the initial weighting coefficients in the interval of the training signal and selects the updated weighting coefficients in the interval of the data signal. Then the weight switching unit outputs the selected initial weighting coefficients and updated weighting coefficients as the weighting coefficients. A synthesizing unit weights the baseband received signals with the weighting coefficients and then sums them up.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a receiving technology. It particularlyrelates to a receiving method and a receiving apparatus which controls aweighting coefficient for synthesizing radio signals received by aplurality of antennas.

2. Description of the Related Art

In wireless communication, it is in general desired to effectively uselimited frequency resources. In order to use the frequency resourceseffectively, radio waves of same frequency are, for example, utilized asrepeatedly as possible in short-range. In this case, however,communication quality degrades because of cochannel interference causedby a radio base station or mobile terminal closely located, whichutilizes the same frequency. As one technology for preventing suchcommunication quality degradation deriving from the cochannelinterference, the adaptive array antenna technology can be named.

In the adaptive array antenna technology, signals received by aplurality of antennas are respectively weighted with different weightingcoefficients and synthesized. The weighting coefficients are adaptivelyupdated so that an error signal between a signal to be transmitted andthe signal after the synthesis might be small. Here, the signal to betransmitted is determined based on the signal after synthesis. In orderto update the weighting coefficients adaptively, the RLS (RecursiveLeast Squares) algorithm, the LMS (Least Mean Squares) algorithm or thelike is utilized. The RLS algorithm generally converges at high speed.The RLS algorithm, however, requires a high speed or a huge arithmeticcircuit since computation performed is very complicated. The LMSalgorithm can be realized with a simpler arithmetic circuit than that ofthe RLS algorithm. However, the convergence speed thereof is low.

Related Art List

1. Japanese Patent Application Laid-open No. 2002-26788

In utilizing the adaptive array antenna for a radio mobile terminal, itis suitable to use the LMS algorithm for updating weightingcoefficients, since it is desirable that an arithmetic circuit is small.However, the convergence speed of the LMS algorithm is low in general.Thus, if it is desired to delay received signals to be synthesized untilthe LMS algorithm converges, processing delay becomes large andtherefore it is possibly impossible to use the adaptive array antenna ina real time application such as TV conference system where permissibledelay time is limited. On the other hand, a response characteristicgenerally degrades if the weighting coefficients at the timing where theLMS algorithm has not converged yet in order to diminish the processingdelay.

SUMMARY OF THE INVENTION

The inventor of the present invention has made the present invention inview of the foregoing circumstances and an object thereof is to providea receiver having simple arithmetic circuits, of which the processingdelay is small. It is also an object of the present invention to providea receiver of which the response characteristic hardly degrades even inthe case the weighting coefficients have not converged yet. Moreover, itis also an object of the present invention to provide a receiver whichcan switch a plural types of weighting coefficients.

A preferred embodiment according to the present invention relates to areceiver. This receiver includes: an input unit which inputs a pluralityof signals on which a processing is to be performed; a switching unitwhich switches a plurality of weighting coefficients by which theplurality of inputted signals are multiplied between a plurality offirst weighting coefficients to be temporarily utilized and a pluralityof second weighting coefficients which have higher adaptabilities; acontroller which instructs the switching unit to switch the weightingcoefficients between the plurality of first weighting coefficients andthe plurality of second weighting coefficients; and a synthesizer whichsynthesizes results of multiplications, where the multiplications areperformed on the plurality of inputted signals and the plurality ofweighting coefficients.

The plurality of weighting coefficients include (A, B, C, D) of whichthe number of terms is equal to that of the plurality of signals, wherethe results of multiplications between them and (X1, Y1), (X2, Y2)become (AX1, BY1) and (CX2, DY2). The plurality of weightingcoefficients also include (A, B) of which the number of terms isdifferent from that of the plurality of signals, where the results ofmultiplications become (AX1, BY1) and (AX2, BY2).

The receiver described above enables to acquire a responsecharacteristic optimal in each timing by switching the weightingcoefficients which have different characteristics.

Another preferred embodiment of the present invention also relates to areceiver. The receiver includes: an input unit which inputs a pluralityof signals on which a processing is to be performed; a switching unitwhich switches a plurality of weighting coefficients by which theplurality of inputted signals are multiplied between a plurality offirst weighting coefficients and a plurality of second weightingcoefficients; a controller which instructs the switching unit to switchthe weighting coefficients between the plurality of first weightingcoefficients and the plurality of second weighting coefficients in aprescribed interval, where the plurality of signals are inputted in asequential manner during the interval; and a synthesizer whichsynthesizes results of multiplications, where the multiplications areperformed on the plurality of inputted signals and the plurality ofweighting coefficients.

The “sequential manner” merely means that the known received signal issequential. As long as the signals are inputted sequentially, the timelength does not necessarily need to be long but may be short. Moreover,the sequential manner here may include a case where the signals areinputted in a discrete manner in accordance with a certain rule, if theapparatus recognizes the rule. That is, the “sequential manner” hereincludes every case where the receiver can recognize the manner ofinputting the signals as “sequential” one.

The plurality of first weighting coefficients may be set in a mannerthat, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

The receiver may further include: a weighting coefficient updating unitwhich updates a plurality of third weighting coefficients adaptivelybased on the plurality of inputted signals; a gap estimator whichestimates gaps between the plurality of first weighting coefficients andthe plurality of third weighting coefficients by performing acorrelation processing between at least one of the plurality of inputtedsignals and a known signal; and a gap compensator which generates theplurality of second weighting coefficients by compensating the pluralityof third weighting coefficients based on the estimated gaps.

The signals inputted during the prescribed interval in the sequentialmanner may include signals having different characteristics and thecontroller may instruct to switch the weighting coefficients between thefirst weighting coefficients and the second weighting coefficients whenit is detected a shift point where the characteristics of the signalschange. The controller may input sequentially the plurality of thirdweighting coefficients updated in the weight coefficient updating unitand may instruct the switching unit to switch the weighting coefficientsbetween the first weighting coefficients and the second weightingcoefficients when fluctuation of the plurality of third weightingcoefficients converges within a prescribed range.

The receiver described above enables to acquire a responsecharacteristic optimal in each time by switching the weightingcoefficients which have different characteristics during the interval.

Still, another preferred embodiment according to the present inventionrelates to a receiving method. This method includes: inputting aplurality of signals on which a processing is to be performed; switchinga plurality of weighting coefficients by which the plurality of inputtedsignals are multiplied between a plurality of first weightingcoefficients to be temporarily utilized and a plurality of a secondweighting coefficients which have higher adaptabilities; giving aninstruction of switching the weighting coefficients between theplurality of first weighting coefficients and the plurality of secondweighting coefficients; and synthesizing results of multiplications,where the multiplications are performed on the plurality of inputtedsignals and the plurality of weighting coefficients.

Still another preferred embodiment according to the present inventionrelates to a receiving method. This method includes: inputting aplurality of signals on which a processing is to be performed; switchinga plurality of weighting coefficients by which the plurality of inputtedsignals are multiplied between a plurality of first weightingcoefficients and a plurality of second weighting coefficients; giving aninstruction of switching the weighting coefficients between theplurality of first weighting coefficients and the plurality of secondweighting coefficients in a prescribed interval, where the plurality ofsignals are inputted in a sequential manner during the interval; andsynthesizing results of multiplications, where the multiplications areperformed on the plurality of inputted signals and the plurality ofweighting coefficients.

The plurality of first weighting coefficients may be set in a mannerthat, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

The receiving method may further include: updating a plurality of thirdweighting coefficients adaptively based on the plurality of inputtedsignals; estimating gaps between the plurality of first weightingcoefficients and the plurality of third weighting coefficients byperforming a correlation processing between at least one of theplurality of inputted signals and a known signal; and generating theplurality of second weighting coefficients by compensating the pluralityof third weighting coefficients based on the estimated gaps.

The signals inputted during the prescribed interval in the sequentialmanner may include signals having different characteristics. In givingthe instruction of switching the weighting coefficients between thefirst weighting coefficients and the second weighting coefficients, theinstruction may be given when it is detected a shift point where thecharacteristics of the signals change. The plurality of third weightingcoefficients updated may be inputted sequentially in giving theinstruction of switching the weighting coefficients between the firstweighting coefficients and the second weighting coefficients, and theinstruction may be given when fluctuation of the plurality of thirdweighting coefficients converges within a prescribed range.

Yet another preferred embodiment of the present invention relates to aprogram. The program includes: inputting a plurality of signals on whicha processing is to be performed; switching a plurality of weightingcoefficients by which the plurality of inputted signals are multipliedbetween a plurality of first weighting coefficients to be temporarilyutilized and a plurality of a second weighting coefficients which havehigher adaptabilities; giving an instruction of switching the weightingcoefficients between the plurality of first weighting coefficients andthe plurality of second weighting coefficients; and synthesizing resultsof multiplications, where the multiplications are performed on theplurality of inputted signals and the plurality of weightingcoefficients.

Still another preferred embodiment according to the present inventionrelates to a program method. This program includes: inputting aplurality of signals on which a processing is to be performed; switchinga plurality of weighting coefficients by which the plurality of inputtedsignals are multiplied between a plurality of first weightingcoefficients and a plurality of second weighting coefficients; giving aninstruction of switching the weighting coefficients between theplurality of first weighting coefficients and the plurality of secondweighting coefficients in a prescribed interval, where the plurality ofsignals are inputted in a sequential manner during the interval; andsynthesizing results of multiplications, where the multiplications areperformed on the plurality of inputted signals and the plurality ofweighting coefficients.

The plurality of first weighting coefficients may be set in a mannerthat, as results of multiplications by the plurality of inputtedsignals, a multiplication result corresponding to one signal among theplurality of inputted signals becomes effective. The one signal amongthe plurality of inputted signals may be a signal having a largest valueamong the plurality of inputted signals. The plurality of firstweighting coefficients may be set by utilizing the plurality of secondweighting coefficients which have already been set.

The receiving method may further include: updating a plurality of thirdweighting coefficients adaptively based on the plurality of inputtedsignals; estimating gaps between the plurality of first weightingcoefficients and the plurality of third weighting coefficients byperforming a correlation processing between at least one of theplurality of inputted signals and a known signal; and generating theplurality of second weighting coefficients by compensating the pluralityof third weighting coefficients based on the estimated gaps.

The signals inputted during the prescribed interval in the sequentialmanner may include signals having different characteristics. In givingthe instruction of switching the weighting coefficients between thefirst weighting coefficients and the second weighting coefficients, theinstruction may be given when it is detected a shift point where thecharacteristics of the signals change. The plurality of third weightingcoefficients updated may be inputted sequentially in giving theinstruction of switching the weighting coefficients between the firstweighting coefficients and the second weighting coefficients, and theinstruction may be given when fluctuation of the plurality of thirdweighting coefficients converges within a prescribed range.

It is to be noted that any arbitrary replacement or substitution of theabove-described structural components and the steps, expressionsreplaced or substituted in part or whole between a method and anapparatus as well as addition thereof, and expressions changed to acomputer program, recording medium or the like are all effective as andencompassed by the present embodiments.

Moreover, this summary of the invention does not necessarily describeall necessary features so that the invention may also be sub-combinationof these described features.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a structure of a communication system according to a firstembodiment of the present invention.

FIG. 2 shows a burst format according to the first embodiment of thepresent invention.

FIG. 3 shows a burst format according to the first embodiment of thepresent invention.

FIG. 4 shows a structure of a receiver according to the first embodimentof the present invention.

FIG. 5 shows a structure of a first pre-processing unit shown in FIG. 4.

FIG. 6 shows a structure of the first pre-processing unit shown in FIG.4.

FIG. 7 shows a structure of the first pre-processing unit shown in FIG.4.

FIG. 8 shows a structure of a timing detection unit shown in FIGS. 5, 6and 7.

FIG. 9 shows a structure of a rising edge detection unit shown in FIG.4.

FIG. 10 shows an operation procedure of the rising edge detection unitshown in FIG. 9.

FIG. 11 shows a structure of an antenna determination unit shown in FIG.4.

FIG. 12 shows a structure of a first weight computation unit shown inFIG. 4.

FIG. 13 shows a structure of a gap measuring unit shown in FIG. 4.

FIG. 14 shows a structure of a gap compensating unit shown in FIG. 4.

FIG. 15 shows a structure of a synthesizing unit shown in FIG. 4.

FIG. 16 shows a structure of a receiver according to a second embodimentof the present invention.

FIG. 17 shows a structure of an antenna determination unit shown in FIG.16.

FIG. 18 shows a structure of a gap measuring unit shown in FIG. 16.

FIG. 19 shows a structure of a frequency error estimation unit shown inFIG. 18.

FIG. 20 shows a structure of a gap measuring unit shown in FIG. 16.

DETAILED DESCRIPTION OF THE INVENTION

The invention will now be described based on the preferred embodiments,which do not intend to limit the scope of the present invention, butexemplify the invention. All of the features and the combinationsthereof described in the embodiment are not necessarily essential to theinvention.

FIRST EMBODIMENT

The first embodiment of the present invention relates to a receiverprovided with an adaptive array antenna which receives radio signalswith a plurality of antennas as burst signals and synthesizes thereceived signals with weighting them respectively by different weightingcoefficients. The burst signal is composed of a known training signalwhich is disposed in the head part thereof and a data signal. Thereceiver, in order to reduce processing delay, synthesizes the receivedsignals by weighting them with the weighting coefficients withoutscarcely delaying them. The weighting coefficients are updated by theLMS algorithm one after another. As the weighting coefficients in thetraining signal interval, however, precedently prepared weightingcoefficients of an omni antenna pattern are utilized since it is oftenthe case that the weighting coefficients have not converged yet in theinitial period of the training signal interval. Weighting coefficientsof adaptive array antenna pattern, which are updated by the LMSalgorithm, are utilized as the weighting coefficients in the interval ofthe data signal.

FIG. 1 shows a communication system including a transmitter 100 and areceiver 106 according to the first embodiment of the present invention.The transmitter 100 includes a modulator 102, a RF unit 104, and anantenna 132. The receiver 106 includes a first antenna 134 a, a secondantenna 134 b, a n-th antenna 134 n, a RF unit 108, a signal processingunit 110, and a demodulator 112. Here the first antenna 134 a, thesecond antenna 134 b and the n-th antenna 134 n are generically namedantennas 134.

The modulator 102 modulates an information signal to be transmitted andgenerates the transmission signal (hereinafter one signal included inthe transmission signal is also called as a “symbol”). Any arbitrarymodulation scheme may be utilized, such as QPSK (Quadri Phase ShiftKeying), 16QAM (16 Quadrature Amplitude Modulation), GMSK (Gaussianfiltered Minimum Shift Keying). In the following embodiments, examplesare described where the QPSK is utilized. Moreover, in a case of a multicarrier communication, the transmitter 100 is provided with theplurality of modulators 102 or inverse Fourier transform units. In acase of a spectrum spreading communication, the modulator 102 isprovided with a spreading unit.

The RF unit 104 transforms the transmission signal into radio frequencysignal. A frequency transformation unit, a power amplifier, a frequencyoscillator and so forth are included therein.

The antenna 132 of the transmitter 100 transmits the radio frequencysignals. The antenna may have arbitrary directivity and the number ofthe antennas may also be arbitrary.

The antennas 134 of the receiver 106 receive the radio frequencysignals. In this embodiment, the number of the antennas 134 is n. Whenit is described in this embodiment that the receiver has a n-thcomponent thereof, it means that the number of the components providedto the receiver 106 is same as the number of the antennas 134, where thefirst, second, . . . n-th component basically performs same operation inparallel.

The RF unit 108 transforms the radio frequency signals into basebandreceived signals 300. A frequency oscillator and so forth are providedto the RF unit 108. In a case of the multi carrier communication, the RFunit 108 is provided with a Fourier transform unit. In a case of thespectrum spreading communication, the RF unit 108 is provided with adespreading unit.

The signal processing unit 110 synthesizes the baseband received signals330 with respectively weighting by the weighting coefficients andcontrols each weighting coefficient adaptively.

The demodulator 112 demodulates the synthesized signals and performsdecision on the transmitted information signal. The demodulator 112 mayalso be provided with a delay detection circuit or a carrier recoverycircuit for coherent detection.

FIG. 2 and FIG. 3 show other burst formats respectively utilized indifferent communication systems corresponding to the communicationsystem shown in FIG. 1. Training signals and data signals included inthe burst signals are also shown in those figures. FIG. 2 shows a burstformat utilized in a traffic channel of the Personal Handyphone System.A preamble is placed in initial 4 symbols of the burst, which isutilized for timing synchronization. The signals of the preamble and aunique word can serve as a known signal for the signal processing unit110, therefore the signal processing unit 110 can utilize the preambleand the unique word as the training signal. Data and CRC both followingafter the preamble and the unique word are unknown for the signalprocessing unit 110 and correspond to the data signal.

FIG. 3 shows a burst format utilized in a traffic channel of the IEEE802.11a, which is one type of wireless LAN (Local Area Network). TheIEEE 802.11a employs OFDM (Orthogonal Frequency Division Multiplexing)modulation scheme. In the OFDM modulation scheme, the size of theFourier transform and the number of the symbols of the guard intervalare summated and the summation forms a unit. It is to be noted that thisone unit is described as an OFDM symbol in this embodiment. A preambleis placed in initial 4 OFDM symbols of the burst, which is mainlyutilized for timing synchronization and carrier recovery. The signals ofthe preamble can serve as a known signal for the signal processing unit110, therefore the signal processing unit 110 can utilize the preambleas the training signal. Header and Data both following after thepreamble are unknown for the signal processing unit 110 and correspondto the data signal.

FIG. 4 shows a structure of the receiver 106 shown in FIG. 1. The RFunit 108 includes a first pre-processing unit 114 a, a secondpre-processing unit 114 b, . . . and a n-th pre-processing unit 114 n,which are generically named pre-processing units 114. The signalprocessing unit 110 includes: a first BB input unit 116 a, a second BBinput unit 116 b, . . . and a n-th BB input unit 116 n which aregenerically named BB input units 116; a synthesizing unit 118; a firstweight computation unit 120 a, a second weight computation unit 120 b, .. . and a n-th weight computation unit 120 n which are generically namedweight computation units 120; a rising edge detection unit 122; acontrol unit 124; a training signal memory 126; an antenna determinationunit 10; an initial weight data setting unit 12; a gap measuring unit14, a gap compensating unit 16; a weight switching unit 18. Thedemodulator 112 includes a synchronous detection unit 20, a decisionunit 128 and a summing unit 130.

Moreover the signals utilized in the receiver 106 include: a firstbaseband received signal 300 a, a second baseband received signal 300 b,. . . and n-th baseband received signal 300 n which are genericallynamed the baseband received signals 300; a training signal 302; acontrol signal 306; an error signal 308; a first control weightingcoefficient 310 a, a second control weighting coefficient 310 b, . . .and a n-th control weighting coefficient 310 n which are genericallynamed control weighting coefficients 310; an antenna selection signal314; a gap error signal 316; a first updated weighting coefficient 318a, a second updated weighting coefficient 318 b, . . . and a n-thupdated weighting coefficient 318 n which are generically named updatedweighting coefficients 318; a first initial weighting coefficient 320 a,a second initial weighting coefficient 320 b, . . . and a n-th initialweighting coefficient 320 n which are generically named initialweighting coefficients 320; and a first weighting coefficient 322 a, asecond weighting coefficient 322 b, . . . and a n-th weightingcoefficient 322 n which are generically named weighting coefficients322.

The pre-processing units 114 translates the radio frequency signals intothe baseband received signals 300.

The rising edge detection unit 122 detects the starts of the burstsignals which serve as a trigger of the operation of the signalprocessing unit 110 from the baseband received signals 300. The timingsof the detected starts of the burst signals are informed to the controlunit 124. The control unit 124 computes timings when the interval of thetraining signal 302 ends, based on the timings of the starts of theburst signals. These timings are notified to each unit as controlsignals 306 in accordance with necessity.

The antenna determination unit 10 measures the electric power of eachbaseband received signal 300 after the interval of the training signal302 is started in order to select one antenna 134 to be made effectivein the interval of the training signal 302 and then determines the onebaseband received signal 300 of which the electric power becomes islargest. Moreover, the antenna determination unit 10 outputs thisinformation as the antenna selection signal 314.

The initial weight data setting unit 12 sets the weighting coefficients322 utilized in the interval of the training signal 302 as the initialweighting coefficients 320. The initial weight data setting unit 12makes only one initial weighting coefficient 302 effective by settingthe value of the one initial weighting coefficient 320 as 1 and bysetting the values of the other weighting coefficients 320 as 0. The oneinitial weighting coefficient 320 to be made effective is decidedaccording to the antenna selection signal 314.

The training signal memory 126 stores the training signal 302 andoutputs the training signal in accordance with necessity.

The weight computation unit 120 updates the control weightingcoefficients 310 based on the baseband received signals 300 andafter-mentioned error signal 308 by the LMS algorithm.

The gap measuring unit 14, based on the baseband received signals 300and the training signal 302, estimates the gap between the results of asynthesis processing performed in the after-mentioned synthesizing unit118, wherein one result is acquired by performing the synthesizingprocessing on the initial weighting coefficients 320 and basebandreceived signals 300 and the other is acquired by performing thesynthesizing processing on the control weighting coefficients 310 andthe baseband received signals 300. The synthesis result acquired byutilizing the initial weighting coefficients 320 is the basebandreceived signal 300 as it is, which is corresponding to one antenna 134.Therefore following expression (1) can be acquired. Here, it is presumedthat the one antenna 134 is an i-th antenna 134.x_(i)(t)=h _(i) S(t)exp(jΔωt)+m_(i) t  (1)

Here, hi is the response characteristic of the radio interval, S(t) isthe transmission signal, Δω is the frequency offset between thefrequency oscillators of the transmitter 100 and the receiver 106, andni(t) is a noise. On the other hand, a control weighting coefficient 310wi updated from the head region of the burst signal is given by:Σh_(i)w_(i=)1  (2)

Here, it is presumed assumed that the control weighting coefficientshave already converged sufficiently.

By performing the synthesis processing based on the ground of theabove-described expression (2), following result of the synthesisprocessing can be acquired.y(t)=S(t)exp(jΔωt)+n(t)  (3)

By comparing the synthesis results shown in (1) and (3), a gap errorsignal 316C is given by:C=h_(i)  (4)

The gap compensating unit 16 compensates the control weightingcoefficients 310 with the gap error signal 316 and outputs the result ofthe compensation as the updated weighting coefficients 318.

The weight switching unit 18, based on the instruction of the controlsignal 306, selects the initial weighting coefficients 320 in theinterval of the training signal 302 and selects the updated weightingcoefficients 318 in the interval of the data signal. Then, the weightswitching unit 18 outputs them as the weighting coefficients 322.

The synthesizing unit 118 weights the baseband received signals 300 withthe weighting coefficients 322 and then sums them up.

The synchronous detection unit 20 performs synchronous detection on thesynthesized signals and also performs a carrier recovery necessary forthe synchronous detection.

The decision unit 128 decides the transmitted information signal bycomparing the signal acquired by the summation to a pre-determinedthreshold value. The decision may be either hard or soft.

The summing unit 130 generates the error signal 308 based on thedifference value between the synchronous detected signal and the decidedsignal, which is to be utilized in the LMS algorithm in the weightcomputation units 120. In an ideal situation, the error signal becomeszero since the LMS algorithm controls the weighting coefficients 310 sothat the error signal 308 might become small.

FIG. 5 to FIG. 7 show various structures of the first pre-processingunit 114 a. The first pre-processing unit 114 a in the receiver 106 canaccept and treat various signals in different communication systems suchas shown in FIG. 2 or FIG. 3, therefore the signal processing unit 110following thereafter can operate ignoring the difference of thecommunication systems. The first pre-processing unit 114 a in FIG. 5 isfor the single carrier communication system shown in FIG. 2 such asPersonal Handyphone System, cellular phone system or the like. The firstpre-processing unit 114 a in FIG. 5 includes a frequency translationunit 136, a quasi synchronous detector 138, an AGC (Automatic GainControl) 140, an AD conversion unit 142, and a timing detection unit144. The first pre-processing unit 114 a shown in FIG. 6 is for thespectrum spreading communication system such as the W-CDMA(Wideband-Code Division Multiple Access) or the wireless LAN implementedin relation to the IEEE 802.11b. In addition to the first pre-processingunit 114 a shown in FIG. 5, that shown in FIG. 6 further includes adespreading unit 172. The first pre-processing unit 114 a is for themulti carrier communication system shown in FIG. 3 such as the IEEE802.11a or the Hiper LAN/2. In addition to the first pre-processing unit114 a shown in FIG. 6, that shown in FIG. 7 further includes a Fouriertransform unit 174.

The frequency translation unit 136 translates the radio frequency signalinto one intermediate frequency signal, a plurality of intermediatefrequency signals or other signals. The quasi synchronous detector 138performs quadrature detection on the intermediate frequency signalutilizing a frequency oscillator and generates a baseband analog signal.Since the frequency oscillator included in the quasi synchronousdetector 138 operates independently from the frequency oscillatorprovided to the transmitter 100, the frequencies between the twooscillators differ from each other.

The AGC 140 automatically controls gains so that the amplitude of thebaseband analog signal might become an amplitude within the dynamicrange of the AD conversion unit 142.

The AD conversion unit 142 converts the baseband analog signal into adigital signal. Sampling interval for converting the baseband analogsignal to the digital signal is generally set to be shorter than symbolinterval in order to constrict the degradation of the signal. Here, thesampling interval is set to the half of the symbol interval(Hereinafter, the signal digitalized with this sampling interval isreferred to as a “high speed digital signal”).

The timing detection unit 144 selects a baseband received signal 300 ofan optimal sampling timing from the high speed digital signals.Alternatively, the timing detection unit 144 generates the basebandreceived signal 300 having the optimal sampling timing by performing asynthesis processing or the like on the high speed digital signals.

The despreading unit 172 shown in FIG. 6 performs correlation processingon the baseband received signal 300 based on a predetermined codeseries. The Fourier transform unit 174 in FIG. 7 performs the Fouriertransform on the baseband received signal 300.

FIG. 8 shows the structure of the timing detection unit 144. The timingdetection unit 144 includes: a first delay unit 146 a, a second delayunit 146 b, . . . and a (n−1)-th delay unit 146 n−1 which aregenerically named delay units 146; a first multiplication unit 150 a, asecond multiplication unit 150 b, a (n−1)-th multiplication unit 150n−1, . . . and a n-th multiplication unit 150 n which are genericallynamed multiplication units 150; a first data memory 152 a, a second datamemory 152 b, a (n−1)-th data memory 152 n−1, . . . a n-th data memory152 n which are generically named data memories 152; a summing unit 154;a decision unit 156; a main signal delay unit 158; and a selecting unit160.

The delay units 146 delay the inputted high speed digital signal for thecorrelation processing. The sampling interval of the high speed digitalsignal is set to half of the symbol interval. However the delay quantityof the delay units 146 is set to the symbol interval, therefore the highspeed digital signal 150 is outputted from every other delay unit 146 tothe multiplication units 150.

The data memories 152 store 1 symbol of each preamble signal for thetiming synchronism.

The multiplication units 150 perform multiplications on the high speeddigital signals and the preamble signals, and the results thereof aresummed up by the summing unit 154.

The decision unit 156 selects an optimal sampling timing based on theresult of the summation. The sampling interval of the high speed digitalsignal is half of the symbol signal and the interval of the high speeddigital signal utilized for the summation is equal to the symbolinterval, therefore there are two types of the summation results forevery other high speed digital signal corresponding to each shiftedsampling timing. The decision unit 156 compares the two types of thesummation results and decides a timing corresponding to larger summationresult as the optimal sampling timing. This decision should notnecessarily be made by comparing the two types of the summation resultsonce, but may be made by comparing them for several times.

The main signal delay unit 158 delays the high speed digital signaluntil the optimal sampling timing is determined by the decision unit156.

The selecting unit 160 selects a baseband received signal 300corresponding to the optimal sampling timing from the high speed digitalsignals. Here one high speed digital signal is selected sequentiallyfrom the two successive high digital speed signals.

FIG. 9 shows the structure of the rising edge detection unit 122included in the signal processing unit 110. The rising edge detectionunit 122 includes a power computation unit 162 and a decision unit 164.The power computation unit 162 computes the received power of eachbaseband received signal 300 and then sums up the received power of eachbaseband received signal to acquire the whole power of the signals whichare received by all the antennas 134.

The decision unit 164 compares the whole received power of the signalswith a predetermined condition and decides that the start of the burstsignal is detected when the condition is satisfied.

FIG. 10 shows the operation of the rising edge detection unit 122. Thedecision unit 164 sets an internal counter T to zero (S10). The powercomputation unit 162 computes the received power from the basebandreceived signals 300 (S12). The determination unit 164 compares thereceived power with a threshold value. When the received power is largerthan the threshold value (Y in S14), the decision unit 164 adds 1 to theT (S16). When the T becomes larger than a predetermined value τ (Y inS18), it is decided that the start of the burst signal is detected. Theprocessing described-above is repeated until the start of the burstsignal is detected (N in S14, N in S18).

FIG. 11 shows the structure of the antenna determination unit 10. Theantenna determination unit 10 includes: a first level measuring unit 22a, a second level measuring unit 22 b, . . . and a n-th level measuringunit 22 n which are generically called level measuring units 22; and aselecting unit 24.

The level measuring units 22 detect the start timing of the burst signalbased on the control signal 306 and measure the electric power of eachbaseband received signal 300 during prescribed interval from the starttiming.

The selecting unit 24 selects the baseband received signal 300 which hasthe largest electric power by comparing the electric power of eachbaseband received signal 300 and then outputs a result as the antennaselection signal 314.

FIG. 12 shows the structure of the first weight computation unit 120 a.The first weight computation unit 120 a includes a switching unit 48, acomplex conjugate unit 50, a main signal delay unit 52, a multiplicationunit 54, a step size parameter memory 56, a multiplication unit 58, asumming unit 60, and a delay unit 62.

The switching unit 48 selects the training signal 302 in the interval ofthe training signals 302 by detecting the start timing of the burstsignal and the end timing of interval of the training signal 302 basedon the control signal 306 and then selects the error signal 308 in theinterval of the data signal.

The main signal delay unit 52 delays the first baseband received signal300 a so that the first baseband received signal 300 a might synchronizewith the timing detected by the rising edge detection unit 122.

The multiplication unit 54 generates a first multiplication result bymultiplying the phase error 308 after complex conjugate transform in thecomplex conjugate unit 50 by the first baseband received signal 300 awhich is delayed by the main signal delay unit 52.

The multiplication unit 58 generates a second multiplication result bymultiplying the first multiplication result by a step size parameterstored in the step size parameter memory 56. The second multiplicationresult is fed back by the delay unit 62 and the summing unit 60 andadded to a new second multiplication result. The result of the summationis then sequentially updated by the LMS algorithm. This summation resultis outputted as the first weighting coefficient 310 a.

FIG. 13 shows the structure of the gap measuring unit 14. The gapmeasuring unit 14 includes a complex conjugate unit 44, a selecting unit64, a buffer unit 66 and a multiplication unit 68.

The selecting unit 64, based on the antenna selection signal 314,selects the baseband received signal 300 corresponding to the oneinitial weighting coefficient 320 which has been made effective in theinterval of the training signal 302.

The buffer unit 66 detects the start timing of the burst signal based onthe control signal 306 and outputs the baseband received signal 300 atthe start timing.

The multiplication unit 68 multiplies the training signal 302 after thecomplex conjugate processing in the complex conjugate unit 44 by the onebaseband received signal 300 outputted from the buffer unit 66 and thenoutputs the gap error signal 316. Here, it is presumed that both thetraining signal 302 and baseband received signal 300 are the head signalof the burst signal.

FIG. 14 shows the structure of the gap compensating unit 16. The gapcompensating unit 16 includes a first multiplication unit 70 a, a secondmultiplication unit 70 b, . . . and a n-th multiplication unit 70 nwhich are generically named multiplication units 70.

The multiplication units 70 detect the end timing of the interval of thetraining signal 302 based on the control signal 306. Then themultiplication units 70 multiply the control weighting coefficients 310by the gap error signal 316 and outputs the updated weightingcoefficients 318.

FIG. 15 shows the structure of the synthesizing unit 118 which isincluded in the signal processing unit 110. The synthesizing unit 118includes: a first delay unit 166 a, a second delay unit 166 b, . . . anda n-th delay unit 166 n which are generically named delay units 166; afirst multiplication unit 168 a, a second multiplication unit 168 b, . .. and a n-th multiplication unit 168 n which are generically namedmultiplication units 168; and a summing unit 170.

Since the delay time of the delay units 166 is from the detection of thehead of the burst signal by the rising edge detection unit 122 untilsetting the weighting coefficients 322 by the initial weight datasetting unit 12 via the weight switching unit 18, the processing delayof the delay units 166 can be ignored in general. Therefore,synthesizing processing with less processing delay can be realized.

The multiplication units 168 multiply the baseband received signals 300which are delayed by the delay units 166 by the weighting coefficients322. The summing unit 170 sums up the whole results of themultiplications by the multiplications units 168.

Hereunder will be described the operation of the receiver 106 having thestructure described above. The signals received by the plurality ofantennas 134 are translated to the baseband received signals 300 by thequadrature detection and so forth. When the rising edge detection unit122 detects the starts of the burst signals from the baseband receivedsignals 300, the interval of the training signal 302 is started. At thestart timing of the interval of the training signal 302, the antennadetermination unit 10 selects the one baseband received signal 300. Thenthe initial weight data setting unit 12 sets the initial weightingcoefficients 320, where the only initial weighting coefficient 320corresponding to the selected baseband received signal 300 is madeeffective.

In the interval of the training signal 302, the weight switching unit 18outputs the initial weighting coefficients 320 as the weightingcoefficients 322 and the synthesizing unit 118 sums up the basebandreceived signals 300 weighting them with the weighting coefficients 322.Meanwhile, the weight computation units 120 update the control weightingcoefficients 310 by the LMS algorithm. In the interval of the datasignal, the gap compensating unit 16 compensates the control weightingcoefficients 310 with the gap error signal 316 computed in the gapmeasuring unit 14 and then outputs them as the updated weightingcoefficients 318. Moreover, the weight switching unit 18 outputs theupdated weighting coefficients 318 as the weighting coefficients 322 andthe synthesizing unit 118 weights the baseband received signals 300 withthe weighting coefficients 322 and sums them up.

According to the first embodiment, the processing delay can be reducedsince the synthesizing processing is performed even in the interval ofthe training signal regardless of the convergence of the weightingcoefficients. Moreover, communications with surrounding radio stationslocated in the vicinity can be realized since the omni antenna patternis utilized for the weighting coefficients in the interval of thetraining signal. The weighting coefficients can be smoothly switchedbetween the omni antenna pattern and the adaptive array antenna pattern.

SECOND EMBODIMENT

In the second embodiment, same as the first embodiment, received signalsare weighted with weighting coefficients and synthesized. The processingdelay hardly occurs since the switching is performed between the omniantenna pattern which is precedently prepared and the adaptive arraypattern updated by the LMS algorithm. In the first embodiment, theswitching of the weighting coefficients between two types is performedin an undifferentiated manner at the timing where the training signalincluded in the burst signal ends. On the other hand, in the secondembodiment, the switching of weighting coefficients between two types isperformed adaptively at the timing where the LMS algorithm convergeswithin a predetermined range.

FIG. 16 shows the structure of the receiver 106 according to the secondembodiment. The structure thereof is almost same as the structure of thereceiver 106 shown in FIG. 4. However, the receiver 106 shown in FIG. 16includes a first convergence information 324 a, a second convergenceinformation 324 b, . . . and a n-th convergence information 324 n whichare generically named convergence information 324.

The weight switching unit 18 shown in FIG. 4 performs the switchingoperation in a manner that the initial weighting coefficient 320 isselected in the interval of the training signal 302 and the updatedweighting coefficient is selected in the interval of the data signal,wherein the end timing of the interval of the initial weightingcoefficients 320 severs as a trigger for the weight switching unit 18.On the other hand, the weight switching unit 18 utilizes the timingwhere the control weighting coefficients 310 converge in the weightcomputation units 120 (hereinafter this timing is referred to as a“convergence timing”). The convergence timing is generated by thecontrol unit 124 when the fluctuation of the control weightingcoefficients 310 caused by updating them converges within in a range,wherein the range is determined precedently. Alternatively, theconvergence timing may be generated by the control unit 124 when theupdated error signal 308 becomes within a range, wherein the range ispredetermined for the error signal 308.

The control unit 124 notifies the convergence timing to each unit inaccordance with the necessity, and each unit performs its assignedprocessing according to the convergence timing.

FIG. 17 shows the structure of the antenna determination unit 10. Theantenna determination unit 10 includes a switching unit 72, a levelmeasuring unit 74, a storage 76 and a selecting unit 24.

The switching unit 72 switches the plurality of baseband receivedsignals 300 at a prescribed timing and outputs one baseband receivedsignal 300. The switching may be performed on the plurality of burstsignals.

The level measuring unit 74 measures the electric power of the basebandreceived signal 300 selected by the switching unit 72. Being differentfrom the antenna determination unit 10 shown in FIG. 11, the electricpower of the plurality of baseband received signals 300 is not measuredat a time but measured for every baseband received signal 300 one byone, therefore the size of an arithmetic circuit for the level measuringunit 74 can be diminished.

The storage 76 stores the computed electric power of the basebandreceived signal 300.

FIG. 18 shows the structure of the gap measuring unit 14. The gapmeasuring unit 14 shown in FIG. 18 is structured by adding a frequencyerror estimation unit 78, an interval measuring unit 80, amultiplication unit 82, a complex number transformation unit 84, acomplex conjugate unit 86 and a multiplication unit 88 to the gapmeasuring unit 14 shown in FIG. 13.

In the second embodiment, being different from the first embodiment, thetiming where the weight computation units 120 start updating the controlweight coefficients 310 is the head of the long preamble of the burstformat shown in FIG. 3. The control weighting coefficient 310 wi updatedfrom the head of the long preamble is given by the expression (5) below.Here, it is presumed that the control weighting coefficients 310 haveconverged sufficiently.Σh _(i) w _(i) exp(jΔωsT)=1  (5)

Here, sT is the time length of a short preamble interval. By performingthe synthesizing processing based on the expression (5), the synthesisresult is given by:y(t)=S(t)exp(jΔωt)exp(−jΔωsT)+n(t)  (6)

By comparing these expressions, the gap error signal 316C can beexpressed as follows.C=h _(i) exp(−jΔωsT)  (7)

The frequency error estimation unit 78 estimates a frequency error Δωbased on the baseband received signals 300. The interval measuring unit80 measures the time sT of the short preamble interval based on thetraining signal 302.

The multiplication unit 82 multiplies the frequency error by the time ofthe short preamble interval and acquires the phase error in the intervalof the short preamble. This phase error is transformed to a complexnumber by the complex number transformation unit 84 and a complexconjugate processing is performed thereon by the complex conjugate unit86.

The multiplication unit 88 multiplies, by the above-described phaseerror, the result of the multiplication processing on the one basebandreceived signal 300 and the complex conjugated training signal 302, andthen generates the gap error signal 316.

FIG. 19 shows the structure of the frequency error estimation unit 78.The frequency error estimation unit 78 includes: a first main signaldelay unit 26 a, a second main signal delay unit 26 b, . . . and a n-thmain signal delay unit 26 n which are generically named main signaldelay units 26; a first multiplication unit 28 a, a secondmultiplication unit 28 b, . . . and a n-th multiplication unit 28 nwhich are generically named multiplication units 28; a first delay unit30 a, a second delay unit 30 b, . . . and a n-th delay unit 30 n whichare generically named delay units 30; a first complex conjugate unit 32a, a second complex conjugate unit 32 b, . . . and a n-th complexconjugate unit 32 n which are generically named complex conjugate units32; a first multiplication unit 34 a, a second multiplication unit 34 b,. . . and a n-th multiplication unit 34 n which are generically namedmultiplication units 34; an averaging unit 36; a phase transformationunit 38; and a training signal memory 42.

The multiplication units 28 acquires a received signal Zi(t) which doesnot include transmission signal component by multiplying the basebandreceived signals 300 delayed in the main signal delay units 26 by thetraining signal 302 after the complex conjugate transform. The receivedsignal Zi(t) is given by: $\begin{matrix}\begin{matrix}{{Z_{i}(t)} = {{x_{i}(t)}S*(t)}} \\{= {h_{i}{\exp\left( {{j\Delta\omega}\quad t} \right)}}}\end{matrix} & (8)\end{matrix}$

Here, it is assumed that a noise is sufficiently small and therefore thenoise is ignored.

The delay units 30 and the complex conjugate units 32 delay the Zi(t)and then transform the Zi(t) to the complex conjugate. The Zi(t)transformed to the complex conjugate is multiplied by the original Zi(t)in the multiplication units 34. The result Ai of the multiplication isgiven by: $\begin{matrix}\begin{matrix}{{A_{i}(t)} = {{Z_{i}(t)}{Z_{i}^{*}\left( {t - T} \right)}}} \\{= {\exp({j\Delta\omega t})}}\end{matrix} & (9)\end{matrix}$

Here, the delay time of the delay units 30 is set to the symbol intervalT.

The averaging unit 36 averages the multiplication results correspondingto each antenna. The multiplication results of which the time is shiftedmay also be utilized.

The phase transformation unit 38 transforms the averaged multiplicationresult A to a phase signal B by utilizing an arc tangent ROM.B=ΔωT  (10)

FIG. 20 shows the structure of a gap measuring unit 14 which isdifferent from the gap measuring unit 14 shown in FIG. 18. The gapmeasuring unit 14 shown in FIG. 20 is structured by adding a counterunit 90, a multiplication unit 92, a complex number transformation unit94, a summing unit 96, a summing unit 98 and a division unit 40 to thegap measuring unit 14 shown in FIG. 18. In the gap measuring unit 14shown in FIG. 18, the multiplication of the baseband received signals300 by the training signal 302 is performed only on the head signal ofthe burst signal. On the other hand, in the gap measuring unit 14 shownin FIG. 20, the multiplications are performed during prescribed time andthe results thereof are averaged.

The summing unit 98 sums up the results of the multiplications by themultiplications unit 96 during prescribed time interval (hereinafterreferred to as “averaging time”) in order to average the results of themultiplications of the baseband received signals 300 by the trainingsignal 302.

The counter unit 90 counts up the symbol intervals in order to acquirethe phase error corresponding to the averaging time based on thefrequency error outputted from the frequency error estimation unit 78.The multiplication unit 92 acquires the phase error corresponding toeach counter value by respectively multiplying each counter value by thefrequency error. The phase errors are transformed to complex numbers inthe complex number transformation unit 94 and are summed up in thesumming unit 96 within the averaging time.

The division unit 40 divides the results of the multiplications summedup by the summing unit 98 with the phase errors summed up by the summingunit 96. The succeeding processings are same as those of the gapmeasuring unit 14 shown in FIG. 18.

Hereunder will be described the operation of the receiver 106 having thestructure described above. The signals received by the plurality ofantennas 134 are transformed to the baseband received signals 300 by thequadrature detection and so forth. When the rising edge detection unit122 detects the start timings of the burst signals from the basebandreceived signals 300, the interval of the training signal 302 isstarted. At the start timing of the interval of the training signal 302,the antenna determination unit 10 selects the one baseband receivedsignal 300 and the initial weight data setting unit 12 sets the initialweighting coefficients 320 among which only the one initial weightingcoefficient 320 corresponding to the selected baseband received signal300 is made effective. Thereafter, the weight switching unit 18 outputsthe initial weighting coefficients 320 as the weighting coefficients 322and the synthesizing unit 118 weights the baseband received signals 300with the weighting coefficients 322 and sums them up.

Meanwhile, the weight computation units 120 update the control weightingcoefficients 310 by the LMS algorithm. When the control weightingcoefficients 310 converge within the prescribed range, the gapcompensating unit 16 compensates the control weighting coefficients 310with the gap error signal 316 computed in the gap measuring unit 14according to the instruction from the control unit 124 and then outputsthem as the updated weighting coefficients 318. Moreover, weightswitching unit 18 outputs the updated weighting coefficients 318 as theweighting coefficients 322 and the synthesizing unit 118 weights thebaseband received signals 300 with the weighting coefficients 322 andsums them up.

According to the second embodiment, the synthesis processing isperformed regardless of the convergence of the weighting coefficientseven in the interval of the training signal. Therefore, the processingdelay can be reduced. Moreover, in the case that the adaptive algorithmconverges during the training signal interval, the responsecharacteristic can be improved by reflecting it to the weightingcoefficients. This is because the switching of the weightingcoefficients between two types is performed based on the convergencetiming of the adaptive algorithm.

Although the present invention has been described by way of exemplaryembodiments, it should be understood that many changes and substitutionsmay be made by those skilled in the art without departing from the scopeof the present invention which is defined by the appended claims.

In the embodiments, the initial weight data setting unit 12 sets theeffective value for the initial weighting coefficient 320 for the onebaseband received signal 300 selected by the antenna determination unit10, which has the largest electric power, and the unit 12 sets the valuewhich is not effective for the other initial weighting coefficients 320.The initial weighting coefficients 320, however, do not necessarily needto be set based on the electric power. For example, one fixed initialweighting coefficient 320 may be set to the effective value and theother initial weighting coefficients 320 may be set to the value that isnot effective. In that case, the antenna determination unit 10 becomesunnecessary.

In the embodiments, the initial weight data setting unit 12 sets theeffective value for the initial weighting coefficient 320 for the onebaseband received signal 300 selected by the antenna determination unit10, which has the largest electric power, and the unit 12 sets the valuewhich is not effective for the other initial weighting coefficients 320.It is, however, not necessarily required to set the weighting of theomni antenna pattern for the initial weighting coefficients 320. Forexample, the setting may be performed on the updated weightingcoefficients 318 or the control weighting coefficients 310 which areutilized in the already received burst signal. When the fluctuation ofthe radio transmission environment is small, it is estimated that thissetting will not cause a serious degradation of the responsecharacteristic.

In the embodiments, the weight computation units 120 utilize the LMSalgorithm as the adaptive algorithm. However, another algorithm such asthe RLS algorithm may be utilized. Moreover, the weighting coefficientsmay not be updated. That is, it is sufficient if the adaptive algorithmis selected in accordance with the estimated radio transmissionenvironment, the size of arithmetic circuits or the like.

In the first embodiment, the rising edge detection unit 122 computes theelectric power of the baseband received signals 300 and detects therising edge of the burst signal based on the computation result. Therising edge of the burst signal may be, however, detected byimplementing another structure. For example, the rising edge may bedetected by a matched filter which is shown as the structure of thetiming detection unit 144. That is, it is sufficient if the rising edgeof the burst signal is detected accurately.

In the first embodiment, the training signal interval is the time wherethe initial weighting coefficients 320 are changed into the weightingcoefficients 322. However, the time does not need to be limited to theinterval of the training signal. For example, the time may be shorterthan the interval of the training signal. That is, the time can be setaccording to the length of the interval of the training signal and tothe required estimation accuracy.

In the second embodiment, the delay time of the delay units 30 which areincluded in the frequency error estimating unit 78 is set to 1 symbol.The delay time, however, is not limited to 1 symbol. For example, thedelay time may be 2 symbols or may be symbols in the interval betweenthe start and end of the training signal. That is, it is sufficient ifan optimum delay time of the delay units 30 is decided in accordancewith the stability of the frequency oscillator and with the requiredaccuracy of the frequency offset estimation.

1.-24. (canceled)
 25. A method for processing a received signal, themethod comprising: receiving, from a transmitter, a first signal from afirst antenna terminal and a second signal from a second antennaterminal wherein the first signal and the second signal each contains atleast one packet having a training interval and a data interval; using afirst set of weighting factors to select the first signal or the secondsignal; correlating the first and second signals with a stored referencesignal in a period during which the first set of weighting factors isused, to determine a second set of weighting factors; and applying thesecond set of weighting factors to an array synthesizer, after theperiod during which the first set of weighting factors is used.
 26. Amethod according to claim 25, further receiving, from the transmitter, athird signal from a third antenna terminal wherein the third signalcontains at least one packet having a training interval and a datainterval.
 27. A method according to claim 25, further comprising:measuring a channel response of the first signal or the second signal;and using the measured channel response to generate a gap error signalfor correcting a phase gap in an output signal of the array synthesizer.28. A method according to claim 27, further comprising updating thesecond set of weighting factors, based on the gap error signal.
 29. Areceiver comprising: an input unit configured to receive, from atransmitter, a first signal from a first antenna terminal and a secondsignal from a second antenna terminal wherein the first signal and thesecond signal each contains at least one packet having a traininginterval and a data interval; an initial weight data setting unitconfigured to use a first set of weighting factors to select the firstsignal or the second signal; a weight computation unit configured tocorrelate the first and second signals with a stored reference signal ina period during which the first set of weighting factors is used, todetermine a second set of weighting factors; and a weight switching unitconfigured to apply the second set of weighting factors to an arraysynthesizer, after the period during which the first set of weightingfactors is used.
 30. A receiver according to claim 29, wherein the inputunit is configured to receive, from the transmitter, a third signal froma third antenna terminal wherein the third signal contains at least onepacket having a training interval and a data interval.
 31. A receiveraccording to claim 29, further comprising a gap measuring unitconfigured to measure a channel response of the first signal or thesecond signal and to use the measured channel response to generate a gaperror signal for correcting a phase gap in an output signal of the arraysynthesizer.
 32. A receiver according to claim 31, further comprising agap compensating unit configured to update the second set of weightingfactors, based on the gap error signal.